Maisie and Wendy are very, very different in style, so its hatd to think of a name to "match" both!
Wendy was popular in the 50s and 60 and its contempraries would e names like Dawn, Tracey, Linda, Janet...
Maisie is much more modern and Cutesy and goes with names like Poppy, Rosie etc.
I think you need to choose a very vlassic name such as Elizabeth, Charlotte, Catherine... or a very unusual name. Darcy is a good suggestion, although I probably wouldn't choose another name with a final "y" sound. How about Pearl?